Fluid accumulation and infection at the site of a wound can significantly hinder wound healing. Fluid accumulation can exert a detrimental mass effect upon adjacent tissue and compress vital anatomy or structures. Infection can result in tissue morbidity, rejection, fever, gangrene and even death.
Background discussion regarding fluid accumulation and tissue infection follows, in turn. That certain information is presented as background herein should not, however, be taken as indication that the present invention does not predate it.
With respect to fluid accumulation, if detected before significant damage occurs, it can often be treated by simple surgical intervention. For instance, lancing and/or drain insertion or implantation may provide adequate and continuing therapeutic relief.
Impedance measurement has been employed to measure volumetric changes of the body in certain applications. U.S. Pat. No. 4,805,621 to Heinze et al. discloses a system adapted to measure body tissue impedance, particularly to set the rate of a pacemaker by reference to volumetric measurement of a beating heart and thorax during respiration movement. Heinze neither discloses or suggests the use of local impedance differences to locate or monitor indicia negative of proper wound healing.
Regarding infection, it is well established that infection can be effectively treated by antibiotics. Also, antibiotics can be effectively administered prophylactically to avoid infection. However, this approach may not be desired for reasons ranging from drug interaction, to bacterial resistance to antibiotics. Regardless, it is desired and often necessary to repeatedly check, examine or monitor an area for infection—especially prior to administering antibiotics.
It is also known that infected tissue presents at a higher temperature relative to uninfected tissue. U.S. Pat. No. 6,135,968 to Brounstein teaches the use of temperature sensors affixed to an insulative support to fit over or be adhered to a probe (such as a finger) for accessing internal body locations via body orifices to effect temperature-based examinations. The preferred embodiments include two discrete temperature sensing regions allowing for comparative analysis of tissue temperature. As stated in the patent, an important function of the temperature sensor support in all embodiments of the invention is to insulate a temperature sensing patch from the fingertip of the user and thereby improve the accuracy of the sensed temperatures by isolating temperature sensed by the sensing patch from the influence of heat emanating from the user's fingertip. Closed cell polyurethane foam with a thickness of about 1 to 2 millimeters is disclosed as a suitably pliable and insulative material for the temperature sensor support.
By comparing the temperature of near-by healthy tissue with that of a suspect site, a diagnosis can be made as to the existence of abnormal subsurface tissue activity such as the growth of malignant tumors, benign neoplasms, infections and/or inflammations. The devices involved and examination techniques disclosed are, however, by no means suited for long-term infection monitoring.
One recently disclosed device is, however, suited for sustained monitoring of wounds for infection. In a Nov. 5, 2001 issue of Medical Industry Today, a story was run reporting that the University of Rochester had taken steps toward creating a bandage that will change color depending on what kind of bacteria may be present in a wound. The bandage was disclosed as capable of giving an instant diagnosis as to whether the wound may require special care or what kind of antibiotics would work best in treating it. A silicon-based sensor is employed to differentiate between Gram-positive and negative bacteria. Indication of further application include similar sensors to identify several other types of bacteria, with particular focus on research directed toward antibiotic resistant strains. As embodied in a “smart bandage,” the sensor is said to function in connection with a type of molecule called “lipid A” on the surface of Gram-negative bacteria. When a complementary molecule linked to or part of the sensor binds to lipid A, the sensor changes color.
The article indicates that color change of the sensor is subtle and could be missed by a human eye. Accordingly, reading by an ancillary device is discussed. One embodiment envisioned for the bandage includes an array of dozens of different bacterial sensors that will change color dramatically enough so a glance inspection will alert the user to a serious infection.
Potential non-medical applications are also disclosed in which, for example, a drinking vessel or wrapping around a package of ground beef would change color to caution a user in the event of the presence of certain bacteria. Further potential applications envisioned include providing early warning against biowarfare.
The breakthrough described in association with the development of the bandage was detecting and identifying a single, distinct species of bacteria. Further development possibilities were linked in the article to finding molecules that detect other bacteria. In any case, the silicon sensors only have bacteria-specific wound monitoring capability. Furthermore, even if the prophesized sensor arrays come into being, they will only detect such forms of bacteria corresponding specifically to the array elements. Accordingly the smart bandage approach taught in the article lacks general applicability. To remedy this, the article merely suggests searching for molecules capable of detecting other bacteria to add functionality in a piecemeal fashion.